Mountain Weather

Diffwys weather forecast.

750 m summit in Eryri (Snowdonia). 8 forecast days covering wind, cloud, rain and temperature, updated 21 September 2026 at 16:08 UTC.

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Confidence: Medium
Overall hill weather62/100Mixed
Wind5-20 mph westerly Gusts15-25 mph Feels like6 to 10°C PrecipitationUp to around 2 mm Cloud-free summit estimate45% Cloud base through day600-900 m Freezing levelAbove summit DaylightSunrise 06:59 · Sunset 19:17 · 12.3 hours daylight

The day on the hill

Frequent summit cloud on Diffwys: summit wind broadly 5-20 mph, with gusts 15-25 mph at times (a moderate breeze).

Cloud & views

Cloud base mostly around 600–900 m through daylight. Summit cloud is likely, but brief clear spells remain possible if the cloud sits higher than expected.

Cloud-height uncertainty could put the summit in or out of cloud. Clear spells may be difficult to time.

Very little direct sunshine is likely, with extensive cloud.

Rain & temperature

The ground is likely to be wet after recent rain. Little or no rain is forecast.

Forecast confidence

Cloud height remains uncertain, especially where it is close to summit level. Cloud-height uncertainty could put the summit in or out of cloud, even where forecasts agree on the wider cloud cover.

Sunshine context Model-grid estimate, not summit sunshine

The surrounding model grid indicates 0 h of sunshine. This is not a forecast of time in sunshine on the summit. Use the cloud and views outlook above for the conditions on this mountain.

Early
0 h
Midday
0 h
Later
0 h

Overnight forecast: 17:00–08:00 (UK local time), in Wild camping below.

Morning · 08:00–12:00 Mixed Summit winds around 5-15 mph. Gusts around 15-25 mph are possible on exposed ground.
61/100
Afternoon · 12:00–17:00 Mixed Summit winds around 5-15 mph. Gusts around 10-20 mph are possible on exposed ground.
62/100

Compare an early start with later conditions. The main forecast above covers the day in more detail.

Overnight · 17:00–08:00Wild campingBetaAbout 1.8 mm is forecast, with rain liable to affect both pitching and packing up. 64/100Mixed · 600 m View detailsHide details
Night beginning Monday 21 September 2026

Full overnight outlook

Open-hillside camping looks reasonable overall around 600 m (64/100). Light winds are expected on open ground, though local shelter and exposure still matter. Around 1.8 mm is forecast, with rain liable to affect both pitching and packing up. Condensation risk is high near 300 and 600 m, so a wet pack-up is possible. Ventilation will matter.

Overnight rain1.8 mm Open ground · 600 m9 mph · gusts 14 mph Morning pack-upDampness possible Sleeping-bag warmthISO comfort rating about 10°C or lower

Moon overnight

Waxing gibbous moon

Illuminated disc
78%
Moonrise
17:38 BST
Moonset
01:32 next morning BST

Extensive cloud may limit moonlight. Illumination describes the sunlit part of the Moon, not brightness at your pitch.

Overnight window: 21 Sep, 17:00 BST to 22 Sep, 08:00 BST. Approximate open-horizon times; hills can hide the Moon. Still take a headtorch.

Elevation reference (open ground)

300 m64/100 · reasonable
Wind / gust
7 mph / 12 mph
Typical / low
13.0°C / 12.2°C
In cloud
0% of modelled night
Condensation
High
600 m64/100 · reasonable
Wind / gust
9 mph / 14 mph
Typical / low
13.0°C / 12.2°C
In cloud
0% of modelled night
Condensation
High

Warmth planning: As a broad starting point, consider a 2-season bag with an ISO/EN comfort rating at or below about 10°C. Allow more margin if you sleep cold or expect fatigue, and use an adequate insulated mat. Dampness is possible, so keep the sleep system dry and ensure its insulation remains effective if damp.

Open-hillside reference. A sheltered pitch may be calmer; cols and ridges may be much windier. Tent design and the exact pitch still matter. Read about sleeping-bag comfort ratings, pitching in strong winds or using the wild-camping forecast.

Did this match your night?Share a quick observation to help improve this beta forecast.Give feedback

Approximate height is enough, please do not share an exact wild-camp location.

Daytime · exposed rockClimbing & scramblingBetaWet rock is likely. Poor26/100 View detailsHide details
Generic exposed-rock guidance

Full climbing & scrambling outlook

Conditions for exposed scrambling look poor (26/100). Rain during the climbing period is likely to leave rock wet and more slippery. The mapped summit rock is Mudstone and siltstone (Gamlan Formation). Often positive when dry, but smooth, polished or slabby sections can become markedly more slippery when damp. Cloud may also make route-finding and retreat harder.

Rock surfaceWet rock likelyPeak gust18 mphRain0.2 mm
Main factorswet rock likelymuch of the route may be in cloud
Mapped summit rock Mudstone and siltstone Gamlan Formation
Origin
Sedimentary
Rock family
Slate or mudstone
Mapping
BGS Geology 50K · 1:50,000
Rock-response profile
Moderate confidence
View the summit BGS record

Often positive when dry, but smooth, polished or slabby sections can become markedly more slippery when damp. Summit-point bedrock mapping; the actual route may cross different rock, superficial deposits, polish, lichen or seepage.

Generic exposed scrambling terrain; mapped summit-point bedrock is included where available, but route grade, exact rock, polish, drainage and escape options remain unresolved. Contains British Geological Survey materials © UKRI 2026. How to use the climbing and scrambling forecast.

Did this match your experience?Tell us about the rock surface and wind to help improve this beta forecast.Give feedback

A broad surface report is enough; you do not need to identify a particular route.

Overnight · Aurora, stars & meteorsAfter darkBetaCloud is likely to obscure much of the sky. Reduced visibility may obscure faint objects. Moonlight washes out fainter stars. View forecastClose forecast

After dark: aurora and stargazing

Night beginning 2026-09-21. All times are UK local time.

Stargazing

Poor sky conditions during the best available spell: 21 Sep, 21:15 BST to 22:00 BST.

Cloud is likely to obscure much of the sky. Reduced visibility may obscure faint objects. Moonlight washes out fainter stars.

Moon-free dark sky: 22 Sep, 01:25 BST to 05:05 BST.

Sky conditions through the night
Fully dark periods. Conditions can change between forecast hours.
TimeViewing conditions
21 Sep, 21:15 BST to 22:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Reduced visibility may obscure faint objects. Moonlight washes out fainter stars.

21 Sep, 22:00 BST to 23:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Reduced visibility may obscure faint objects. Moonlight washes out fainter stars.

21 Sep, 23:00 BST to 22 Sep, 00:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Reduced visibility may obscure faint objects.

22 Sep, 00:00 BST to 01:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Reduced visibility may obscure faint objects.

22 Sep, 01:00 BST to 02:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Reduced visibility may obscure faint objects.

22 Sep, 02:00 BST to 03:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Reduced visibility may obscure faint objects.

22 Sep, 03:00 BST to 04:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Reduced visibility may obscure faint objects.

22 Sep, 04:00 BST to 05:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Rain may interrupt viewing. Reduced visibility may obscure faint objects.

22 Sep, 05:00 BST to 05:05 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Reduced visibility may obscure faint objects.

Moon, darkness and meteor showers

Gibbous moon, about 78% illuminated.

Moonrise around 21 Sep, 17:40 BST.

Moonset around 22 Sep, 01:25 BST.

Full darkness: 21 Sep, 21:15 BST to 22 Sep, 05:05 BST.

Moon times assume an open horizon. Hills can hide the Moon sooner. Moon-free does not mean cloud-free.

Southern Taurids are active on this night. Activity may be much lower away from the peak.

  • Draconids: peak around 9 October 2026.
  • Southern Taurids: peak around 10 October 2026.
  • Orionids: peak around 21 October 2026.
  • Northern Taurids: peak around 12 November 2026.
  • Leonids: peak around 18 November 2026.
  • Geminids: peak around 14 December 2026.
  • Ursids: peak around 22 December 2026.

Dates from the Royal Observatory Greenwich. Activity dates do not guarantee visible meteors. Look across a broad, dark sky, not only north.

Darkness of the surroundings

Estimated darkness rank 470 of 980 assessed peaks (1 is darkest), based on surrounding artificial light in 2021. This is not a measurement of tonight’s sky.

2021 artificial-light baseline, not measured sky brightness or a Bortle class. Changes to lighting, blue-rich LEDs, terrain screening, atmospheric scattering and cloud-reflected light are not resolved. Similar ranks are not meaningfully distinct. Darkness is not a recommendation to climb a summit at night.

VIIRS nighttime lights: Earth Observation Group, Payne Institute for Public Policy, Colorado School of Mines. Reprocessed by OpenGeoHub/OpenLandMap. Cropped and ranked by Mountain Weather.

Sky-weather grades exclude light pollution, terrain and thin haze. They are not mountain safety ratings. Check the mountain and camping forecast separately. Accessible lower viewpoints may be a better choice than summits.

Recommended kit for this dayWeather-aware packing prompts, plus your core hillwalking kitView kit

For a day hillwalk, not a complete route-specific checklist. Carry navigation and backup you can use, warm and waterproof layers, suitable footwear, food and water, a headtorch, emergency shelter, first aid and a way to call for help. Snow, ice, technical terrain and overnight trips need additional equipment and skills.

Does the weather shape your plans?Optional hill-user research. One answer helps; further questions are up to you.Take part

Help the Mountain Decisions Project understand how forecasts influence hill days, including when plans stay the same. Findings will be shared publicly as summaries, not individual responses.

This is about Diffwys on Monday 21 September 2026. It asks about intentions, not whether you actually went out. No name or account is needed.

Open the questions to take part.

About the research and your privacy · Already been out? Share that experience instead

Confidence: Medium
Overall hill weather62/100Mixed
Wind5-15 mph southwesterly Gusts10-20 mph Feels like8 to 12°C PrecipitationLittle or none Cloud-free summit estimate50% Cloud base through day600-900 m Freezing levelAbove summit DaylightSunrise 07:01 · Sunset 19:15 · 12.2 hours daylight

The day on the hill

Frequent summit cloud on Diffwys: summit wind broadly 5-15 mph, with gusts 10-20 mph at times (light winds).

Cloud & views

Cloud base mostly around 600–900 m through daylight. Cloud is likely to cover the top for much of the day, though a brief clearance is possible during the evening.

Cloud-height uncertainty could put the summit in or out of cloud. Clear spells may be difficult to time.

Any sunshine may be confined to lower ground or breaks away from the summit.

Rain & temperature

Little or no rain is forecast.

Forecast confidence

Cloud height remains uncertain, especially where it is close to summit level. Cloud-height uncertainty could put the summit in or out of cloud, even where forecasts agree on the wider cloud cover.

Cloud-free timing: Around 40% early, improving to around 70% later.

Sunshine context Model-grid estimate, not summit sunshine

The surrounding model grid indicates 3.5 h of sunshine. This is not a forecast of time in sunshine on the summit. Use the cloud and views outlook above for the conditions on this mountain.

Early
0 h
Midday
1.7 h
Later
1.7 h

Overnight forecast: 17:00–08:00 (UK local time), in Wild camping below.

Morning · 08:00–12:00 Mixed Summit winds around 5-15 mph. Gusts around 10-20 mph are possible on exposed ground.
60/100
Afternoon · 12:00–17:00 Mixed Summit winds around 5-15 mph. Gusts around 5-15 mph are possible on exposed ground.
65/100

Compare an early start with later conditions. The main forecast above covers the day in more detail.

Overnight · 17:00–08:00Wild campingBetaA broadly promising night on a well-chosen pitch. 86/100Excellent · 600 m View detailsHide details
Night beginning Tuesday 22 September 2026

Full overnight outlook

Open-hillside camping looks promising overall around 600 m (86/100). It may be breezy on open ground, with gusts near 25 mph. Little overnight rain is forecast. Some condensation is possible overnight.

Overnight rain0.0 mm Open ground · 600 m10 mph · gusts 25 mph Morning pack-upDampness possible Sleeping-bag warmthISO comfort rating about 8°C or lower

Moon overnight

Waxing gibbous moon

Illuminated disc
86%
Moonrise
17:56 BST
Moonset
02:50 next morning BST

Views of the Moon may come and go through cloud breaks. Illumination describes the sunlit part of the Moon, not brightness at your pitch.

Overnight window: 22 Sep, 17:00 BST to 23 Sep, 08:00 BST. Approximate open-horizon times; hills can hide the Moon. Still take a headtorch.

Elevation reference (open ground)

300 m88/100 · very good
Wind / gust
8 mph / 21 mph
Typical / low
12.8°C / 11.5°C
In cloud
0% of modelled night
Condensation
Moderate
600 m86/100 · promising
Wind / gust
10 mph / 25 mph
Typical / low
12.8°C / 11.5°C
In cloud
0% of modelled night
Condensation
Moderate

Warmth planning: As a broad starting point, consider a 2-season bag with an ISO/EN comfort rating at or below about 8°C. Allow more margin if you sleep cold or expect fatigue, and use an adequate insulated mat. Dampness is possible, so keep the sleep system dry and ensure its insulation remains effective if damp.

Open-hillside reference. A sheltered pitch may be calmer; cols and ridges may be much windier. Tent design and the exact pitch still matter. Read about sleeping-bag comfort ratings, pitching in strong winds or using the wild-camping forecast.

Did this match your night?Share a quick observation to help improve this beta forecast.Give feedback

Approximate height is enough, please do not share an exact wild-camp location.

Daytime · exposed rockClimbing & scramblingBetaCloud may complicate route-finding and retreat. Mixed66/100 View detailsHide details
Generic exposed-rock guidance

Full climbing & scrambling outlook

Conditions for exposed scrambling look fair (66/100). Rock is likely to be mostly dry, though seepage and shaded holds are not resolved. The mapped summit rock is Mudstone and siltstone (Gamlan Formation). Often positive when dry, but smooth, polished or slabby sections can become markedly more slippery when damp. Cloud may also make route-finding and retreat harder.

Rock surfaceProbably dryPeak gust14 mphRain0.0 mm
Main concernmuch of the route may be in cloud
Mapped summit rock Mudstone and siltstone Gamlan Formation
Origin
Sedimentary
Rock family
Slate or mudstone
Mapping
BGS Geology 50K · 1:50,000
Rock-response profile
Moderate confidence
View the summit BGS record

Often positive when dry, but smooth, polished or slabby sections can become markedly more slippery when damp. Summit-point bedrock mapping; the actual route may cross different rock, superficial deposits, polish, lichen or seepage.

Generic exposed scrambling terrain; mapped summit-point bedrock is included where available, but route grade, exact rock, polish, drainage and escape options remain unresolved. Contains British Geological Survey materials © UKRI 2026. How to use the climbing and scrambling forecast.

Did this match your experience?Tell us about the rock surface and wind to help improve this beta forecast.Give feedback

A broad surface report is enough; you do not need to identify a particular route.

Overnight · Aurora, stars & meteorsAfter darkBetaCloud is likely to obscure much of the sky. Moonlight washes out fainter stars. View forecastClose forecast

After dark: aurora and stargazing

Night beginning 2026-09-22. All times are UK local time.

Stargazing

Poor sky conditions during the best available spell: 22 Sep, 21:10 BST to 22:00 BST.

Cloud is likely to obscure much of the sky. Moonlight washes out fainter stars.

Moon-free dark sky: 23 Sep, 02:40 BST to 05:05 BST.

Sky conditions through the night
Fully dark periods. Conditions can change between forecast hours.
TimeViewing conditions
22 Sep, 21:10 BST to 22:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Moonlight washes out fainter stars.

22 Sep, 22:00 BST to 23:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Moonlight washes out fainter stars.

22 Sep, 23:00 BST to 23 Sep, 00:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Moonlight washes out fainter stars.

23 Sep, 00:00 BST to 01:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Reduced visibility may obscure faint objects. Moonlight washes out fainter stars.

23 Sep, 01:00 BST to 02:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Rain may interrupt viewing.

23 Sep, 02:00 BST to 03:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Reduced visibility may obscure faint objects.

23 Sep, 03:00 BST to 04:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Reduced visibility may obscure faint objects.

23 Sep, 04:00 BST to 05:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Rain may interrupt viewing. Reduced visibility may obscure faint objects.

23 Sep, 05:00 BST to 05:05 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Rain may interrupt viewing. Reduced visibility may obscure faint objects.

Moon, darkness and meteor showers

Gibbous moon, about 85% illuminated.

Moonrise around 22 Sep, 17:55 BST.

Moonset around 23 Sep, 02:40 BST.

Full darkness: 22 Sep, 21:10 BST to 23 Sep, 05:05 BST.

Moon times assume an open horizon. Hills can hide the Moon sooner. Moon-free does not mean cloud-free.

Southern Taurids are active on this night. Activity may be much lower away from the peak.

  • Draconids: peak around 9 October 2026.
  • Southern Taurids: peak around 10 October 2026.
  • Orionids: peak around 21 October 2026.
  • Northern Taurids: peak around 12 November 2026.
  • Leonids: peak around 18 November 2026.
  • Geminids: peak around 14 December 2026.
  • Ursids: peak around 22 December 2026.

Dates from the Royal Observatory Greenwich. Activity dates do not guarantee visible meteors. Look across a broad, dark sky, not only north.

Darkness of the surroundings

Estimated darkness rank 470 of 980 assessed peaks (1 is darkest), based on surrounding artificial light in 2021. This is not a measurement of tonight’s sky.

2021 artificial-light baseline, not measured sky brightness or a Bortle class. Changes to lighting, blue-rich LEDs, terrain screening, atmospheric scattering and cloud-reflected light are not resolved. Similar ranks are not meaningfully distinct. Darkness is not a recommendation to climb a summit at night.

VIIRS nighttime lights: Earth Observation Group, Payne Institute for Public Policy, Colorado School of Mines. Reprocessed by OpenGeoHub/OpenLandMap. Cropped and ranked by Mountain Weather.

Sky-weather grades exclude light pollution, terrain and thin haze. They are not mountain safety ratings. Check the mountain and camping forecast separately. Accessible lower viewpoints may be a better choice than summits.

Recommended kit for this dayWeather-aware packing prompts, plus your core hillwalking kitView kit

For a day hillwalk, not a complete route-specific checklist. Carry navigation and backup you can use, warm and waterproof layers, suitable footwear, food and water, a headtorch, emergency shelter, first aid and a way to call for help. Snow, ice, technical terrain and overnight trips need additional equipment and skills.

Does the weather shape your plans?Optional hill-user research. One answer helps; further questions are up to you.Take part

Help the Mountain Decisions Project understand how forecasts influence hill days, including when plans stay the same. Findings will be shared publicly as summaries, not individual responses.

This is about Diffwys on Tuesday 22 September 2026. It asks about intentions, not whether you actually went out. No name or account is needed.

Open the questions to take part.

About the research and your privacy · Already been out? Share that experience instead

Confidence: Medium
Overall hill weather53/100Mixed
Wind10-30 mph northwesterly Gusts30-40 mph Feels like2 to 6°C PrecipitationAround 5-10 mm Cloud-free summit estimate75% Cloud base through day600-1,700 m Freezing levelAbove summit DaylightSunrise 07:02 · Sunset 19:13 · 12.2 hours daylight

The day on the hill

On Diffwys: summit wind broadly 10-30 mph, with gusts 30-40 mph at times (strong winds).

Things to watch

Thunderstorms are possible during the morning. Avoid committing to exposed ridges if storms begin to build.

If a thunderstorm develops, sudden gusts and heavy rain can change conditions quickly.

Wind & exposure

Much calmer lower down - generally 5-15 mph in the valley, rising towards the tops.

Cloud & views

Cloud base around 600–900 m in the morning, lifting to 800–1100 m around midday and 1400–1700 m by late afternoon. The top is likely to drift in and out of cloud, with the best chance of a view from around midday into the evening.

Cloud-height uncertainty could put the summit in or out of cloud. Clear spells may be difficult to time.

Cloud may hang lower on northwestern slopes and lift somewhat on the southeastern side, but local terrain can differ. Sunny spells are possible away from summit cloud, but may not reach the top while it is in cloud.

Rain & temperature

Some rain is likely, totalling around 5-10 mm, but its timing and local amounts are uncertain. Forecast models differ on summit wind strength: around 21-29 mph at walker height, with gusts 30-40 mph.

Forecast confidence

Cloud height remains uncertain, especially where it is close to summit level. Exposed tops may feel chilly in the wind.

A windproof layer will help, with an extra warm layer for stops. If clothing gets wet, you can cool more quickly.

Keep a dry warm layer protected. Buffeting may affect balance on exposed ground, particularly near ridges and edges.

Thunderstorm timing is inherently uncertain and may shift by several hours.

Cloud-free timing: Around 35% early, improving to around 95% later.

Sunshine context Model-grid estimate, not summit sunshine

The surrounding model grid indicates 8 h of sunshine. This is not a forecast of time in sunshine on the summit. Use the cloud and views outlook above for the conditions on this mountain.

Early
1 h
Midday
3 h
Later
3 h

Overnight forecast: 17:00–08:00 (UK local time), in Wild camping below.

Morning · 08:00–12:00 Poor Summit winds around 20-30 mph early in the morning, easing to 10-20 mph later. Gusts around 30-40 mph are possible on exposed ground. Buffeting may affect balance on exposed ground, particularly near ridges and edges. Summit cloud is more persistent early in this period, with better prospects later. Rain is forecast during this period. Rain is possible during the morning, but forecast models disagree on whether it will fall.
22/100
Afternoon · 12:00–17:00 Good Rain eases compared with the morning. Summit winds around 10-20 mph. Gusts around 20-30 mph are possible on exposed ground. Summit cloud is more persistent early in this period, with better prospects later.
84/100

Compare an early start with later conditions. The main forecast above covers the day in more detail.

Overnight · 17:00–08:00Wild campingBetaA broadly very good night on a well-chosen pitch. 91/100Excellent · 600 m View detailsHide details
Night beginning Wednesday 23 September 2026

Full overnight outlook

Open-hillside camping looks very good overall around 600 m (91/100). It may be breezy on open ground, with gusts near 20 mph. Little overnight rain is forecast.

Overnight rain0.0 mm Open ground · 600 m9 mph · gusts 22 mph Morning pack-upNo wet signal Sleeping-bag warmthISO comfort rating about 6°C or lower

Moon overnight

Waxing gibbous moon

Illuminated disc
92%
Moonrise
18:09 BST
Moonset
04:08 next morning BST

Clear spells may allow a view of the Moon. Illumination describes the sunlit part of the Moon, not brightness at your pitch.

Overnight window: 23 Sep, 17:00 BST to 24 Sep, 08:00 BST. Approximate open-horizon times; hills can hide the Moon. Still take a headtorch.

Elevation reference (open ground)

300 m92/100 · very good
Wind / gust
8 mph / 18 mph
Typical / low
8.4°C / 8.1°C · much of the night
In cloud
0% of modelled night
Condensation
Low
600 m91/100 · very good
Wind / gust
9 mph / 22 mph
Typical / low
8.4°C / 8.1°C · much of the night
In cloud
0% of modelled night
Condensation
Low

Warmth planning: As a broad starting point, consider a 3-season bag with an ISO/EN comfort rating at or below about 6°C. Allow more margin if you sleep cold or expect fatigue, and use an adequate insulated mat. Dampness is possible, so keep the sleep system dry and ensure its insulation remains effective if damp.

Open-hillside reference. A sheltered pitch may be calmer; cols and ridges may be much windier. Tent design and the exact pitch still matter. Read about sleeping-bag comfort ratings, pitching in strong winds or using the wild-camping forecast.

Did this match your night?Share a quick observation to help improve this beta forecast.Give feedback

Approximate height is enough, please do not share an exact wild-camp location.

Daytime · exposed rockClimbing & scramblingBetaModerate thunderstorm risk. Avoid exposed rock if storms develop. Wet rock is likely. Gusts near 35 mph may affect balance on exposed rock. Poor0/100 View detailsHide details
Generic exposed-rock guidance

Full climbing & scrambling outlook

Conditions for exposed scrambling look very poor (0/100). Rain during the climbing period is likely to leave rock wet and more slippery. The mapped summit rock is Mudstone and siltstone (Gamlan Formation). Often positive when dry, but smooth, polished or slabby sections can become markedly more slippery when damp. Gusts may reach about 35 mph. Crosswinds can make exposed ridges substantially more serious. Moderate thunderstorm risk, broadly during the morning. Avoid committing to exposed ground if storms develop.

Rock surfaceWet rock likelyPeak gust37 mphRain5.5 mm
Main factorsmoderate thunderstorm risk on exposed groundgusts around 35 mphwet rock likely
Mapped summit rock Mudstone and siltstone Gamlan Formation
Origin
Sedimentary
Rock family
Slate or mudstone
Mapping
BGS Geology 50K · 1:50,000
Rock-response profile
Moderate confidence
View the summit BGS record

Often positive when dry, but smooth, polished or slabby sections can become markedly more slippery when damp. Summit-point bedrock mapping; the actual route may cross different rock, superficial deposits, polish, lichen or seepage.

Generic exposed scrambling terrain; mapped summit-point bedrock is included where available, but route grade, exact rock, polish, drainage and escape options remain unresolved. Contains British Geological Survey materials © UKRI 2026. How to use the climbing and scrambling forecast.

Did this match your experience?Tell us about the rock surface and wind to help improve this beta forecast.Give feedback

A broad surface report is enough; you do not need to identify a particular route.

Overnight · Aurora, stars & meteorsAfter darkBetaCloud breaks may offer some views of the stars. Moonlight washes out fainter stars. View forecastClose forecast

After dark: aurora and stargazing

Night beginning 2026-09-23. All times are UK local time.

Stargazing

Mixed sky conditions during the best available spell: 23 Sep, 23:00 BST to 24 Sep, 00:00 BST.

Cloud breaks may offer some views of the stars. Moonlight washes out fainter stars.

Moon-free dark sky: 24 Sep, 04:00 BST to 05:10 BST.

Sky conditions through the night
Fully dark periods. Conditions can change between forecast hours.
TimeViewing conditions
23 Sep, 21:10 BST to 22:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Moonlight washes out fainter stars.

23 Sep, 22:00 BST to 23:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Moonlight washes out fainter stars.

23 Sep, 23:00 BST to 24 Sep, 00:00 BSTMixed sky conditions

Cloud breaks may offer some views of the stars. Moonlight washes out fainter stars.

24 Sep, 00:00 BST to 01:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Moonlight washes out fainter stars.

24 Sep, 01:00 BST to 02:00 BSTPoor sky conditions

Clearer spells are possible, but other forecasts keep much of the sky obscured by cloud.

Forecast models disagree.

24 Sep, 02:00 BST to 03:00 BSTPoor sky conditions

Clearer spells are possible, but other forecasts keep much of the sky obscured by cloud.

Forecast models disagree.

24 Sep, 03:00 BST to 04:00 BSTPoor sky conditions

Clearer spells are possible, but other forecasts keep much of the sky obscured by cloud.

Forecast models disagree.

24 Sep, 04:00 BST to 05:00 BSTPoor sky conditions

Clearer spells are possible, but other forecasts keep much of the sky obscured by cloud.

Forecast models disagree.

24 Sep, 05:00 BST to 05:10 BSTPoor sky conditions

Clearer spells are possible, but other forecasts keep much of the sky obscured by cloud.

Forecast models disagree.

Moon, darkness and meteor showers

Gibbous moon, about 92% illuminated.

Moonrise around 23 Sep, 18:10 BST.

Moonset around 24 Sep, 04:00 BST.

Full darkness: 23 Sep, 21:10 BST to 24 Sep, 05:10 BST.

Moon times assume an open horizon. Hills can hide the Moon sooner. Moon-free does not mean cloud-free.

Southern Taurids are active on this night. Activity may be much lower away from the peak.

  • Draconids: peak around 9 October 2026.
  • Southern Taurids: peak around 10 October 2026.
  • Orionids: peak around 21 October 2026.
  • Northern Taurids: peak around 12 November 2026.
  • Leonids: peak around 18 November 2026.
  • Geminids: peak around 14 December 2026.
  • Ursids: peak around 22 December 2026.

Dates from the Royal Observatory Greenwich. Activity dates do not guarantee visible meteors. Look across a broad, dark sky, not only north.

Darkness of the surroundings

Estimated darkness rank 470 of 980 assessed peaks (1 is darkest), based on surrounding artificial light in 2021. This is not a measurement of tonight’s sky.

2021 artificial-light baseline, not measured sky brightness or a Bortle class. Changes to lighting, blue-rich LEDs, terrain screening, atmospheric scattering and cloud-reflected light are not resolved. Similar ranks are not meaningfully distinct. Darkness is not a recommendation to climb a summit at night.

VIIRS nighttime lights: Earth Observation Group, Payne Institute for Public Policy, Colorado School of Mines. Reprocessed by OpenGeoHub/OpenLandMap. Cropped and ranked by Mountain Weather.

Sky-weather grades exclude light pollution, terrain and thin haze. They are not mountain safety ratings. Check the mountain and camping forecast separately. Accessible lower viewpoints may be a better choice than summits.

Recommended kit for this dayWeather-aware packing prompts, plus your core hillwalking kitView kit

For a day hillwalk, not a complete route-specific checklist. Carry navigation and backup you can use, warm and waterproof layers, suitable footwear, food and water, a headtorch, emergency shelter, first aid and a way to call for help. Snow, ice, technical terrain and overnight trips need additional equipment and skills.

Does the weather shape your plans?Optional hill-user research. One answer helps; further questions are up to you.Take part

Help the Mountain Decisions Project understand how forecasts influence hill days, including when plans stay the same. Findings will be shared publicly as summaries, not individual responses.

This is about Diffwys on Wednesday 23 September 2026. It asks about intentions, not whether you actually went out. No name or account is needed.

Open the questions to take part.

About the research and your privacy · Already been out? Share that experience instead

Confidence: Medium
Overall hill weather81/100Good
Wind10-25 mph southerly Gusts20-30 mph Feels like-4 to 0°C PrecipitationLittle or none Cloud-free summit estimate95% Freezing levelAbove summit DaylightSunrise 07:04 · Sunset 19:10 · 12.1 hours daylight

The day on the hill

Little rain and limited summit cloud on Diffwys: summit wind broadly 10-25 mph, with gusts 20-30 mph at times (a moderate breeze). Patchy mist is possible in sheltered valleys early on.

Cloud & views

Cloud base around 1200–1500 m in the morning, then around 1700–2000 m around midday and 1000–1300 m by late afternoon. The summit is likely to stay mostly clear.

Cloud-height uncertainty could put the summit in or out of cloud. Clear spells may be difficult to time.

Rain & temperature

Little or no rain is forecast. Cold on exposed tops: air temperature broadly 0 to 4°C, feeling around -4 to 0°C in the wind.

Forecast confidence

Cloud height remains uncertain, especially where it is close to summit level. Keep windproof and warm layers readily available.

Cloud-height uncertainty could put the summit in or out of cloud, even where forecasts agree on the wider cloud cover.

Cloud-free timing: Best around midday at about 95%. Lowest later at about 85%.

Sunshine context Model-grid estimate, not summit sunshine

The surrounding model grid indicates 6.3 h of sunshine. This is not a forecast of time in sunshine on the summit. Use the cloud and views outlook above for the conditions on this mountain.

Early
1 h
Midday
3.3 h
Later
1 h

Overnight forecast: 17:00–08:00 (UK local time), in Wild camping below.

Morning · 08:00–12:00 Good Summit winds around 10-20 mph. Gusts around 20-30 mph are possible on exposed ground.
79/100
Afternoon · 12:00–17:00 Good Summit winds around 10-20 mph. Gusts around 20-30 mph are possible on exposed ground.
83/100

Compare an early start with later conditions. The main forecast above covers the day in more detail.

Overnight · 17:00–08:00Wild campingBetaGusts near 30 mph make meaningful shelter important. 54/100Mixed · 600 m View detailsHide details
Night beginning Thursday 24 September 2026

Full overnight outlook

Open-hillside camping looks mixed overall around 600 m (54/100). A lower pitch near 300 m looks more comfortable. Conditions are less suitable by 600 m. Open-ground gusts may reach about 30 mph. Seek meaningful shelter. Peak gusts range from about 25 mph at 300 m to 30 mph at 600 m. A little rain may coincide with pitching or packing up. Pitches near 600 m may spend part of the night in cloud, bringing damp conditions and poor visibility while cloud is present. Condensation risk is high near 600 m. Ventilation will matter.

Overnight rain0.7 mm Open ground · 600 m19 mph · gusts 30 mph Morning pack-upDampness possible Sleeping-bag warmthISO comfort rating about 8°C or lower

Moon overnight

Waxing gibbous moon

Illuminated disc
97%
Moonrise
18:21 BST
Moonset
05:27 next morning BST

Cloud at the reference camping height may hide the Moon. Illumination describes the sunlit part of the Moon, not brightness at your pitch.

Overnight window: 24 Sep, 17:00 BST to 25 Sep, 08:00 BST. Approximate open-horizon times; hills can hide the Moon. Still take a headtorch.

Elevation reference (open ground)

300 m82/100 · promising
Wind / gust
16 mph / 25 mph
Typical / low
10.5°C / 10.1°C
In cloud
0% of modelled night
Condensation
Moderate
600 m54/100 · mixed
Wind / gust
19 mph / 30 mph
Typical / low
10.5°C / 10.0°C · a brief spell
In cloud
53% of modelled night
Condensation
High

Warmth planning: As a broad starting point, consider a 2-season bag with an ISO/EN comfort rating at or below about 8°C. Allow more margin if you sleep cold or expect fatigue, and use an adequate insulated mat. Dampness is possible, so keep the sleep system dry and ensure its insulation remains effective if damp.

Open-hillside reference. A sheltered pitch may be calmer; cols and ridges may be much windier. Tent design and the exact pitch still matter. Read about sleeping-bag comfort ratings, pitching in strong winds or using the wild-camping forecast.

Did this match your night?Share a quick observation to help improve this beta forecast.Give feedback

Approximate height is enough, please do not share an exact wild-camp location.

Daytime · exposed rockClimbing & scramblingBetaRock may be damp or still drying. Good74/100 View detailsHide details
Generic exposed-rock guidance

Full climbing & scrambling outlook

Conditions for exposed scrambling look fair (74/100). Some rock may still be damp or drying, especially on polished slabs and vegetated sections. The mapped summit rock is Mudstone and siltstone (Gamlan Formation). Often positive when dry, but smooth, polished or slabby sections can become markedly more slippery when damp.

Rock surfaceDamp or dryingPeak gust26 mphRain0.0 mm
Main concerndamp or incompletely dried rock possible
Mapped summit rock Mudstone and siltstone Gamlan Formation
Origin
Sedimentary
Rock family
Slate or mudstone
Mapping
BGS Geology 50K · 1:50,000
Rock-response profile
Moderate confidence
View the summit BGS record

Often positive when dry, but smooth, polished or slabby sections can become markedly more slippery when damp. Summit-point bedrock mapping; the actual route may cross different rock, superficial deposits, polish, lichen or seepage.

Generic exposed scrambling terrain; mapped summit-point bedrock is included where available, but route grade, exact rock, polish, drainage and escape options remain unresolved. Contains British Geological Survey materials © UKRI 2026. How to use the climbing and scrambling forecast.

Did this match your experience?Tell us about the rock surface and wind to help improve this beta forecast.Give feedback

A broad surface report is enough; you do not need to identify a particular route.

Overnight · Aurora, stars & meteorsAfter darkBetaClearer spells are possible, but other forecasts keep much of the sky obscured by cloud. View forecastClose forecast

After dark: aurora and stargazing

Night beginning 2026-09-24. All times are UK local time.

Stargazing

Poor sky conditions during the best available spell: 25 Sep, 01:00 BST to 02:00 BST.

Clearer spells are possible, but other forecasts keep much of the sky obscured by cloud.

A bright Moon remains above the horizon through full darkness, washing out fainter stars and meteors.

Sky conditions through the night
Fully dark periods. Conditions can change between forecast hours.
TimeViewing conditions
24 Sep, 21:05 BST to 22:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Moonlight washes out fainter stars.

24 Sep, 22:00 BST to 23:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Moonlight washes out fainter stars.

24 Sep, 23:00 BST to 25 Sep, 00:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Moonlight washes out fainter stars.

25 Sep, 00:00 BST to 01:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Moonlight washes out fainter stars.

25 Sep, 01:00 BST to 02:00 BSTPoor sky conditions

Clearer spells are possible, but other forecasts keep much of the sky obscured by cloud.

Forecast models disagree.

25 Sep, 02:00 BST to 03:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Rain may interrupt viewing. Moonlight washes out fainter stars.

25 Sep, 03:00 BST to 04:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Rain may interrupt viewing. Reduced visibility may obscure faint objects. Moonlight washes out fainter stars.

25 Sep, 04:00 BST to 05:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Rain may interrupt viewing. Reduced visibility may obscure faint objects.

25 Sep, 05:00 BST to 05:10 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Rain may interrupt viewing. Reduced visibility may obscure faint objects.

Moon, darkness and meteor showers

Near-full moon, about 96% illuminated.

Moonrise around 24 Sep, 18:20 BST.

Moonset around 25 Sep, 05:15 BST.

Full darkness: 24 Sep, 21:05 BST to 25 Sep, 05:10 BST.

Moon times assume an open horizon. Hills can hide the Moon sooner. Moon-free does not mean cloud-free.

Southern Taurids are active on this night. Activity may be much lower away from the peak.

  • Draconids: peak around 9 October 2026.
  • Southern Taurids: peak around 10 October 2026.
  • Orionids: peak around 21 October 2026.
  • Northern Taurids: peak around 12 November 2026.
  • Leonids: peak around 18 November 2026.
  • Geminids: peak around 14 December 2026.
  • Ursids: peak around 22 December 2026.

Dates from the Royal Observatory Greenwich. Activity dates do not guarantee visible meteors. Look across a broad, dark sky, not only north.

Darkness of the surroundings

Estimated darkness rank 470 of 980 assessed peaks (1 is darkest), based on surrounding artificial light in 2021. This is not a measurement of tonight’s sky.

2021 artificial-light baseline, not measured sky brightness or a Bortle class. Changes to lighting, blue-rich LEDs, terrain screening, atmospheric scattering and cloud-reflected light are not resolved. Similar ranks are not meaningfully distinct. Darkness is not a recommendation to climb a summit at night.

VIIRS nighttime lights: Earth Observation Group, Payne Institute for Public Policy, Colorado School of Mines. Reprocessed by OpenGeoHub/OpenLandMap. Cropped and ranked by Mountain Weather.

Sky-weather grades exclude light pollution, terrain and thin haze. They are not mountain safety ratings. Check the mountain and camping forecast separately. Accessible lower viewpoints may be a better choice than summits.

Recommended kit for this dayWeather-aware packing prompts, plus your core hillwalking kitView kit

For a day hillwalk, not a complete route-specific checklist. Carry navigation and backup you can use, warm and waterproof layers, suitable footwear, food and water, a headtorch, emergency shelter, first aid and a way to call for help. Snow, ice, technical terrain and overnight trips need additional equipment and skills.

Does the weather shape your plans?Optional hill-user research. One answer helps; further questions are up to you.Take part

Help the Mountain Decisions Project understand how forecasts influence hill days, including when plans stay the same. Findings will be shared publicly as summaries, not individual responses.

This is about Diffwys on Thursday 24 September 2026. It asks about intentions, not whether you actually went out. No name or account is needed.

Open the questions to take part.

About the research and your privacy · Already been out? Share that experience instead

Confidence: Medium
Overall hill weather37/100Poor
Wind15-25 mph westerly Gusts25-35 mph Feels like2 to 6°C PrecipitationAround 5-10 mm Cloud-free summit estimate30% Cloud base through day500-800 m Freezing levelAbove summit DaylightSunrise 07:06 · Sunset 19:08 · 12.0 hours daylight

The day on the hill

A wet day with extensive summit cloud on Diffwys: summit wind broadly 15-25 mph, with gusts 25-35 mph at times (a fresh breeze).

Cloud & views

Cloud base mostly around 500–800 m through daylight. Summit cloud is likely, but brief clear spells remain possible if the cloud sits higher than expected.

Cloud-height uncertainty could put the summit in or out of cloud. Clear spells may be difficult to time.

Cloud may hang lower on western slopes and lift somewhat on the eastern side, but local terrain can differ. Any sunshine may be confined to lower ground or breaks away from the summit.

Drizzle is forecast for much of the day. The forecast total is around 5-10 mm, but local amounts will vary.

Forecast models differ on summit wind strength: around 12-27 mph at walker height, with gusts 17-37 mph.

Forecast confidence

Cloud height remains uncertain, especially where it is close to summit level. Exposed tops may feel chilly in the wind.

A windproof layer will help, with an extra warm layer for stops. If clothing gets wet, you can cool more quickly.

Keep a dry warm layer protected. Forecast models differ on whether meaningful rain reaches the hills during the afternoon and evening.

Sunshine context Model-grid estimate, not summit sunshine

The surrounding model grid indicates 10 h of sunshine. This is not a forecast of time in sunshine on the summit. Use the cloud and views outlook above for the conditions on this mountain.

Cloud may obscure this summit even while the surrounding model grid indicates sunshine. The low cloud-free summit estimate is a reason to be cautious about expecting views.

Early
1.4 h
Midday
4 h
Later
2.6 h

Overnight forecast: 17:00–08:00 (UK local time), in Wild camping below.

Morning · 08:00–12:00 Poor Summit winds around 15-25 mph. Gusts around 25-35 mph are possible on exposed ground. Rain is forecast during this period. Rain is possible during the morning, but forecast models disagree on whether it will fall.
36/100
Afternoon · 12:00–17:00 Poor More rain is expected. Summit winds around 15-25 mph. Gusts around 25-35 mph are possible on exposed ground. Rain is forecast during this period. Some forecast models bring rain during the afternoon, while others keep it mostly dry.
38/100

Compare an early start with later conditions. The main forecast above covers the day in more detail.

Overnight · 17:00–08:00Wild campingBetaAbout 1.2 mm is forecast, with rain possible around pitching time. 64/100Mixed · 600 m View detailsHide details
Night beginning Friday 25 September 2026

Full overnight outlook

Open-hillside camping looks reasonable overall around 600 m (64/100). Light winds are expected on open ground, though local shelter and exposure still matter. Around 1.2 mm is forecast, including rain around pitching time. Condensation risk is high near 300 and 600 m, so a wet pack-up is possible. Ventilation will matter.

Overnight rain1.2 mm Open ground · 600 m9 mph · gusts 18 mph Morning pack-upDampness possible Sleeping-bag warmthISO comfort rating about 4°C or lower

Moon overnight

Near-full moon

Illuminated disc
99%
Moonrise
18:31 BST
Moonset
06:47 next morning BST

Clear spells may allow a view of the Moon. Illumination describes the sunlit part of the Moon, not brightness at your pitch.

Overnight window: 25 Sep, 17:00 BST to 26 Sep, 08:00 BST. Approximate open-horizon times; hills can hide the Moon. Still take a headtorch.

Elevation reference (open ground)

300 m64/100 · reasonable
Wind / gust
8 mph / 15 mph
Typical / low
8.1°C / 7.7°C · much of the night
In cloud
0% of modelled night
Condensation
High
600 m64/100 · reasonable
Wind / gust
9 mph / 18 mph
Typical / low
8.1°C / 7.7°C · much of the night
In cloud
13% of modelled night
Condensation
High

Warmth planning: As a broad starting point, consider a 3-season bag with an ISO/EN comfort rating at or below about 4°C. Allow more margin if you sleep cold or expect fatigue, and use an adequate insulated mat. Dampness is possible, so keep the sleep system dry and ensure its insulation remains effective if damp.

Open-hillside reference. A sheltered pitch may be calmer; cols and ridges may be much windier. Tent design and the exact pitch still matter. Read about sleeping-bag comfort ratings, pitching in strong winds or using the wild-camping forecast.

Did this match your night?Share a quick observation to help improve this beta forecast.Give feedback

Approximate height is enough, please do not share an exact wild-camp location.

Daytime · exposed rockClimbing & scramblingBetaWet rock is likely. Poor3/100 View detailsHide details
Generic exposed-rock guidance

Full climbing & scrambling outlook

Conditions for exposed scrambling look very poor (3/100). Rain during the climbing period is likely to leave rock wet and more slippery. The mapped summit rock is Mudstone and siltstone (Gamlan Formation). Often positive when dry, but smooth, polished or slabby sections can become markedly more slippery when damp. Cloud may also make route-finding and retreat harder.

Rock surfaceWet rock likelyPeak gust30 mphRain8.3 mm
Main factorswet rock likelymuch of the route may be in cloud
Mapped summit rock Mudstone and siltstone Gamlan Formation
Origin
Sedimentary
Rock family
Slate or mudstone
Mapping
BGS Geology 50K · 1:50,000
Rock-response profile
Moderate confidence
View the summit BGS record

Often positive when dry, but smooth, polished or slabby sections can become markedly more slippery when damp. Summit-point bedrock mapping; the actual route may cross different rock, superficial deposits, polish, lichen or seepage.

Generic exposed scrambling terrain; mapped summit-point bedrock is included where available, but route grade, exact rock, polish, drainage and escape options remain unresolved. Contains British Geological Survey materials © UKRI 2026. How to use the climbing and scrambling forecast.

Did this match your experience?Tell us about the rock surface and wind to help improve this beta forecast.Give feedback

A broad surface report is enough; you do not need to identify a particular route.

Overnight · Aurora, stars & meteorsAfter darkBetaClearer spells are possible, but other forecasts keep much of the sky obscured by cloud. View forecastClose forecast

After dark: aurora and stargazing

Night beginning 2026-09-25. All times are UK local time.

Aurora outlook

Slightly raised activity; unlikely to reach this horizon.

A broad activity outlook, not a forecast of a visible display. Cloud and activity can change before the night.

Stargazing

Poor sky conditions during the best available spell: 25 Sep, 22:00 BST to 23:00 BST.

Clearer spells are possible, but other forecasts keep much of the sky obscured by cloud.

A bright Moon remains above the horizon through full darkness, washing out fainter stars and meteors.

Sky conditions through the night
Fully dark periods. Conditions can change between forecast hours.
TimeViewing conditions
25 Sep, 21:05 BST to 22:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Moonlight washes out fainter stars.

25 Sep, 22:00 BST to 23:00 BSTPoor sky conditions

Clearer spells are possible, but other forecasts keep much of the sky obscured by cloud.

Forecast models disagree.

25 Sep, 23:00 BST to 26 Sep, 00:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Moonlight washes out fainter stars.

26 Sep, 00:00 BST to 01:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Moonlight washes out fainter stars.

26 Sep, 01:00 BST to 02:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Rain may interrupt viewing. Moonlight washes out fainter stars.

26 Sep, 02:00 BST to 03:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Rain may interrupt viewing. Moonlight washes out fainter stars.

26 Sep, 03:00 BST to 04:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Rain may interrupt viewing. Moonlight washes out fainter stars.

26 Sep, 04:00 BST to 05:00 BSTPoor sky conditions

Cloud breaks may offer some views of the stars. Reduced visibility may obscure faint objects. Moonlight washes out fainter stars.

26 Sep, 05:00 BST to 05:10 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Reduced visibility may obscure faint objects. Moonlight washes out fainter stars.

Moon, darkness and meteor showers

Near-full moon, about 99% illuminated.

Moonrise around 25 Sep, 18:30 BST.

Moonset around 26 Sep, 06:35 BST.

Full darkness: 25 Sep, 21:05 BST to 26 Sep, 05:10 BST.

Moon times assume an open horizon. Hills can hide the Moon sooner. Moon-free does not mean cloud-free.

Southern Taurids are active on this night. Activity may be much lower away from the peak.

  • Draconids: peak around 9 October 2026.
  • Southern Taurids: peak around 10 October 2026.
  • Orionids: peak around 21 October 2026.
  • Northern Taurids: peak around 12 November 2026.
  • Leonids: peak around 18 November 2026.
  • Geminids: peak around 14 December 2026.
  • Ursids: peak around 22 December 2026.

Dates from the Royal Observatory Greenwich. Activity dates do not guarantee visible meteors. Look across a broad, dark sky, not only north.

Darkness of the surroundings

Estimated darkness rank 470 of 980 assessed peaks (1 is darkest), based on surrounding artificial light in 2021. This is not a measurement of tonight’s sky.

2021 artificial-light baseline, not measured sky brightness or a Bortle class. Changes to lighting, blue-rich LEDs, terrain screening, atmospheric scattering and cloud-reflected light are not resolved. Similar ranks are not meaningfully distinct. Darkness is not a recommendation to climb a summit at night.

VIIRS nighttime lights: Earth Observation Group, Payne Institute for Public Policy, Colorado School of Mines. Reprocessed by OpenGeoHub/OpenLandMap. Cropped and ranked by Mountain Weather.

Sky-weather grades exclude light pollution, terrain and thin haze. They are not mountain safety ratings. Check the mountain and camping forecast separately. Accessible lower viewpoints may be a better choice than summits.

Recommended kit for this dayWeather-aware packing prompts, plus your core hillwalking kitView kit

For a day hillwalk, not a complete route-specific checklist. Carry navigation and backup you can use, warm and waterproof layers, suitable footwear, food and water, a headtorch, emergency shelter, first aid and a way to call for help. Snow, ice, technical terrain and overnight trips need additional equipment and skills.

Does the weather shape your plans?Optional hill-user research. One answer helps; further questions are up to you.Take part

Help the Mountain Decisions Project understand how forecasts influence hill days, including when plans stay the same. Findings will be shared publicly as summaries, not individual responses.

This is about Diffwys on Friday 25 September 2026. It asks about intentions, not whether you actually went out. No name or account is needed.

Open the questions to take part.

About the research and your privacy · Already been out? Share that experience instead

Confidence: Medium
Overall hill weather72/100Good
Wind5-20 mph southwesterly Gusts15-25 mph Feels like-2 to 2°C PrecipitationLittle or none Cloud-free summit estimate70% Cloud base through day600-1,700 m Freezing levelAbove summit DaylightSunrise 07:07 · Sunset 19:05 · 12.0 hours daylight

The day on the hill

On Diffwys: summit wind broadly 5-20 mph, with gusts 15-25 mph at times (light winds).

Cloud & views

Cloud base around 600–900 m in the morning, lifting to 800–1100 m around midday and 1400–1700 m by late afternoon. Summit cloud is extensive early, becoming less frequent later.

Cloud-height uncertainty could put the summit in or out of cloud. Clear spells may be difficult to time.

Sunny spells are possible away from summit cloud, but may not reach the top while it is in cloud.

Rain & temperature

Little or no rain is forecast. Cold on exposed tops: air temperature broadly 2 to 6°C, feeling around -2 to 2°C in the wind.

Forecast confidence

Cloud height remains uncertain, especially where it is close to summit level. Keep windproof and warm layers readily available.

Rain timing may shift by several hours, which could change how much of the main walking period stays dry.

Cloud-free timing: Around 35% early, improving to around 95% later.

Sunshine context Model-grid estimate, not summit sunshine

The surrounding model grid indicates 5.8 h of sunshine. This is not a forecast of time in sunshine on the summit. Use the cloud and views outlook above for the conditions on this mountain.

Early
0 h
Midday
4 h
Later
0 h

Overnight forecast: 17:00–08:00 (UK local time), in Wild camping below.

Morning · 08:00–12:00 Mixed Summit winds around 10-20 mph. Gusts around 15-25 mph are possible on exposed ground.
62/100
Afternoon · 12:00–17:00 Good Summit winds around 5-15 mph. Gusts around 10-20 mph are possible on exposed ground. Rain is possible during the afternoon, but forecast models disagree on whether it will fall.
82/100

Compare an early start with later conditions. The main forecast above covers the day in more detail.

Overnight · 17:00–08:00Wild campingBetaConditions look very good, but forecast uncertainty caps the grade at 82/100. 82/100Good · 600 m View detailsHide details
Night beginning Saturday 26 September 2026

Full overnight outlook

Open-hillside camping looks promising overall around 600 m (82/100). Light winds are expected on open ground, though local shelter and exposure still matter. Little overnight rain is forecast. The coldest temperature falls from about 10.1°C at 300 m to 7.9°C at 600 m. Forecast models are not closely enough agreed for an exceptional grade. The grade is capped at 82/100.

Overnight rain0.0 mm Open ground · 600 m10 mph · gusts 19 mph Morning pack-upNo wet signal Sleeping-bag warmthISO comfort rating about 4°C or lower

Moon overnight

Near-full moon

Illuminated disc
100%
Moonrise
18:42 BST
Moonset
Outside this window

Clear spells may allow a view of the Moon. Illumination describes the sunlit part of the Moon, not brightness at your pitch.

Overnight window: 26 Sep, 17:00 BST to 27 Sep, 08:00 BST. Approximate open-horizon times; hills can hide the Moon. Still take a headtorch.

Elevation reference (open ground)

300 m82/100 · promising
Wind / gust
9 mph / 16 mph
Typical / low
10.2°C / 10.1°C
In cloud
0% of modelled night
Condensation
Low
600 m82/100 · promising
Wind / gust
10 mph / 19 mph
Typical / low
9.6°C / 7.9°C · much of the night
In cloud
0% of modelled night
Condensation
Low

Warmth planning: As a broad starting point, consider a 3-season bag with an ISO/EN comfort rating at or below about 4°C. Allow more margin if you sleep cold or expect fatigue, and use an adequate insulated mat. Dampness is possible, so keep the sleep system dry and ensure its insulation remains effective if damp.

Open-hillside reference. A sheltered pitch may be calmer; cols and ridges may be much windier. Tent design and the exact pitch still matter. Read about sleeping-bag comfort ratings, pitching in strong winds or using the wild-camping forecast.

Did this match your night?Share a quick observation to help improve this beta forecast.Give feedback

Approximate height is enough, please do not share an exact wild-camp location.

Daytime · exposed rockClimbing & scramblingBetaRock may be damp or still drying. Mixed54/100 View detailsHide details
Generic exposed-rock guidance

Full climbing & scrambling outlook

Conditions for exposed scrambling look mixed (54/100). Some rock may still be damp or drying, especially on polished slabs and vegetated sections. The mapped summit rock is Mudstone and siltstone (Gamlan Formation). Often positive when dry, but smooth, polished or slabby sections can become markedly more slippery when damp.

Rock surfaceDamp or dryingPeak gust18 mphRainPossible · 60%
Main concerndamp or incompletely dried rock possible
Mapped summit rock Mudstone and siltstone Gamlan Formation
Origin
Sedimentary
Rock family
Slate or mudstone
Mapping
BGS Geology 50K · 1:50,000
Rock-response profile
Moderate confidence
View the summit BGS record

Often positive when dry, but smooth, polished or slabby sections can become markedly more slippery when damp. Summit-point bedrock mapping; the actual route may cross different rock, superficial deposits, polish, lichen or seepage.

Generic exposed scrambling terrain; mapped summit-point bedrock is included where available, but route grade, exact rock, polish, drainage and escape options remain unresolved. Contains British Geological Survey materials © UKRI 2026. How to use the climbing and scrambling forecast.

Did this match your experience?Tell us about the rock surface and wind to help improve this beta forecast.Give feedback

A broad surface report is enough; you do not need to identify a particular route.

Overnight · Aurora, stars & meteorsAfter darkBetaClearer spells are possible, but other forecasts keep much of the sky obscured by cloud. View forecastClose forecast

After dark: aurora and stargazing

Night beginning 2026-09-26. All times are UK local time.

Aurora outlook

No significant activity expected.

A broad activity outlook, not a forecast of a visible display. Cloud and activity can change before the night.

Stargazing

Poor sky conditions during the best available spell: 26 Sep, 21:00 BST to 22:00 BST.

Clearer spells are possible, but other forecasts keep much of the sky obscured by cloud.

A bright Moon remains above the horizon through full darkness, washing out fainter stars and meteors.

Sky conditions through the night
Fully dark periods. Conditions can change between forecast hours.
TimeViewing conditions
26 Sep, 21:00 BST to 22:00 BSTPoor sky conditions

Clearer spells are possible, but other forecasts keep much of the sky obscured by cloud.

Forecast models disagree.

26 Sep, 22:00 BST to 23:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Rain may interrupt viewing. Reduced visibility may obscure faint objects. Moonlight washes out fainter stars.

26 Sep, 23:00 BST to 27 Sep, 00:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Rain may interrupt viewing. Reduced visibility may obscure faint objects. Moonlight washes out fainter stars.

27 Sep, 00:00 BST to 01:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Rain may interrupt viewing. Moonlight washes out fainter stars.

27 Sep, 01:00 BST to 02:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Moonlight washes out fainter stars.

27 Sep, 02:00 BST to 03:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Moonlight washes out fainter stars.

27 Sep, 03:00 BST to 04:00 BSTPoor sky conditions

Cloud breaks may offer some views of the stars. Reduced visibility may obscure faint objects. Moonlight washes out fainter stars.

27 Sep, 04:00 BST to 05:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Reduced visibility may obscure faint objects. Moonlight washes out fainter stars.

27 Sep, 05:00 BST to 05:15 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Reduced visibility may obscure faint objects. Moonlight washes out fainter stars.

Moon, darkness and meteor showers

Near-full moon, about 100% illuminated.

Moonrise around 26 Sep, 18:45 BST.

Moonset around 27 Sep, 07:55 BST.

Full darkness: 26 Sep, 21:00 BST to 27 Sep, 05:15 BST.

Moon times assume an open horizon. Hills can hide the Moon sooner. Moon-free does not mean cloud-free.

Southern Taurids are active on this night. Activity may be much lower away from the peak.

  • Draconids: peak around 9 October 2026.
  • Southern Taurids: peak around 10 October 2026.
  • Orionids: peak around 21 October 2026.
  • Northern Taurids: peak around 12 November 2026.
  • Leonids: peak around 18 November 2026.
  • Geminids: peak around 14 December 2026.
  • Ursids: peak around 22 December 2026.

Dates from the Royal Observatory Greenwich. Activity dates do not guarantee visible meteors. Look across a broad, dark sky, not only north.

Darkness of the surroundings

Estimated darkness rank 470 of 980 assessed peaks (1 is darkest), based on surrounding artificial light in 2021. This is not a measurement of tonight’s sky.

2021 artificial-light baseline, not measured sky brightness or a Bortle class. Changes to lighting, blue-rich LEDs, terrain screening, atmospheric scattering and cloud-reflected light are not resolved. Similar ranks are not meaningfully distinct. Darkness is not a recommendation to climb a summit at night.

VIIRS nighttime lights: Earth Observation Group, Payne Institute for Public Policy, Colorado School of Mines. Reprocessed by OpenGeoHub/OpenLandMap. Cropped and ranked by Mountain Weather.

Sky-weather grades exclude light pollution, terrain and thin haze. They are not mountain safety ratings. Check the mountain and camping forecast separately. Accessible lower viewpoints may be a better choice than summits.

Recommended kit for this dayWeather-aware packing prompts, plus your core hillwalking kitView kit

For a day hillwalk, not a complete route-specific checklist. Carry navigation and backup you can use, warm and waterproof layers, suitable footwear, food and water, a headtorch, emergency shelter, first aid and a way to call for help. Snow, ice, technical terrain and overnight trips need additional equipment and skills.

Does the weather shape your plans?Optional hill-user research. One answer helps; further questions are up to you.Take part

Help the Mountain Decisions Project understand how forecasts influence hill days, including when plans stay the same. Findings will be shared publicly as summaries, not individual responses.

This is about Diffwys on Saturday 26 September 2026. It asks about intentions, not whether you actually went out. No name or account is needed.

Open the questions to take part.

About the research and your privacy · Already been out? Share that experience instead

Confidence: Unavailable
Overall hill weather46/100Poor
Wind15-30 mph southeasterly Gusts30-40 mph Feels like-2 to 2°C PrecipitationUp to around 2 mm Cloud-free summit estimate35% Cloud base through day500-1,000 m Freezing levelAbove summit DaylightSunrise 07:09 · Sunset 19:03 · 11.9 hours daylight

The day on the hill

Light rain for several hours on Diffwys: summit wind broadly 15-30 mph, with gusts 30-40 mph at times (a fresh breeze).

Wind & exposure

Much calmer lower down - generally 5-15 mph in the valley, rising towards the tops.

Cloud & views

Cloud base around 700–1000 m in the morning, lowering to 500–800 m around midday. Cloud is likely to cover the top for much of the day, though a brief clearance is possible during the morning.

Cloud-height uncertainty could put the summit in or out of cloud. Clear spells may be difficult to time.

Any sunshine may be confined to lower ground or breaks away from the summit. Drizzle is forecast for much of the day.

The forecast total is up to around 2 mm, but local amounts will vary. Cold on exposed tops: air temperature broadly 2 to 6°C, feeling around -2 to 2°C in the wind.

Forecast models differ on summit wind strength. Treat the wind figures as a guide.

Keep windproof and warm layers readily available. If clothing gets wet, you can cool more quickly.

Keep a dry warm layer protected.

Forecast confidence

Overall confidence is unavailable: insufficient comparable wind, rain guidance.

Cloud-free timing: Around 55% early, falling to around 20% later.

Sunshine context Model-grid estimate, not summit sunshine

The surrounding model grid indicates 10.8 h of sunshine. This is not a forecast of time in sunshine on the summit. Use the cloud and views outlook above for the conditions on this mountain.

Cloud may obscure this summit even while the surrounding model grid indicates sunshine. The low cloud-free summit estimate is a reason to be cautious about expecting views.

Early
1.9 h
Midday
4 h
Later
2.9 h

Overnight forecast: 17:00–08:00 (UK local time), in Wild camping below.

Morning · 08:00–12:00 Mixed Summit winds around 15-25 mph. Gusts around 25-35 mph are possible on exposed ground. Summit cloud is more persistent early in this period, with better prospects later. Some forecast models bring rain during the morning, while others keep it mostly dry.
57/100
Afternoon · 12:00–17:00 Poor Summit winds around 20-30 mph. Gusts around 30-40 mph are possible on exposed ground. Rain is forecast during this period.
34/100

Compare an early start with later conditions. The main forecast above covers the day in more detail.

Overnight · 17:00–08:00Wild campingBetaGusts near 30 mph make meaningful shelter important. 54/100Mixed · 600 m View detailsHide details
Night beginning Sunday 27 September 2026

Full overnight outlook

Open-hillside camping looks mixed overall around 600 m (54/100). Open-ground gusts may reach about 30 mph. Seek meaningful shelter. Peak gusts range from about 25 mph at 300 m to 30 mph at 600 m. Wind direction may change substantially during the night. Shelter that works at dusk may be less effective later. Around 1.6 mm is forecast, with rain liable to affect both pitching and packing up. Pitches near 600 m may spend part of the night in cloud, bringing damp conditions and poor visibility while cloud is present. Condensation risk is high near 300 and 600 m. Ventilation will matter.

Overnight rain1.6 mm Open ground · 600 m17 mph · gusts 30 mph Morning pack-upDampness possible Sleeping-bag warmthISO comfort rating about 4°C or lower

Moon overnight

Waning gibbous moon

Illuminated disc
98%
Moonrise
18:53 BST
Moonset
Outside this window

Cloud at the reference camping height may hide the Moon. Illumination describes the sunlit part of the Moon, not brightness at your pitch.

Overnight window: 27 Sep, 17:00 BST to 28 Sep, 08:00 BST. Approximate open-horizon times; hills can hide the Moon. Still take a headtorch.

Elevation reference (open ground)

300 m64/100 · reasonable
Wind / gust
14 mph / 25 mph
Typical / low
11.8°C / 6.0°C · several hours
In cloud
0% of modelled night
Condensation
High
600 m54/100 · mixed
Wind / gust
17 mph / 30 mph
Typical / low
11.0°C / 6.0°C · several hours
In cloud
60% of modelled night
Condensation
High

Warmth planning: As a broad starting point, consider a 3-season bag with an ISO/EN comfort rating at or below about 4°C. Allow more margin if you sleep cold or expect fatigue, and use an adequate insulated mat. Dampness is possible, so keep the sleep system dry and ensure its insulation remains effective if damp.

Open-hillside reference. A sheltered pitch may be calmer; cols and ridges may be much windier. Tent design and the exact pitch still matter. Read about sleeping-bag comfort ratings, pitching in strong winds or using the wild-camping forecast.

Did this match your night?Share a quick observation to help improve this beta forecast.Give feedback

Approximate height is enough, please do not share an exact wild-camp location.

Daytime · exposed rockClimbing & scramblingBetaWet rock is likely. Gusts near 35 mph may affect balance on exposed rock. Poor27/100 View detailsHide details
Generic exposed-rock guidance

Full climbing & scrambling outlook

Conditions for exposed scrambling look poor (27/100). Rain during the climbing period is likely to leave rock wet and more slippery. The mapped summit rock is Mudstone and siltstone (Gamlan Formation). Often positive when dry, but smooth, polished or slabby sections can become markedly more slippery when damp. Gusts may reach about 35 mph. Crosswinds can make exposed ridges substantially more serious. Cloud may also make route-finding and retreat harder.

Rock surfaceWet rock likelyPeak gust34 mphRain1.8 mm
Main factorsgusts around 35 mphwet rock likelymuch of the route may be in cloud
Mapped summit rock Mudstone and siltstone Gamlan Formation
Origin
Sedimentary
Rock family
Slate or mudstone
Mapping
BGS Geology 50K · 1:50,000
Rock-response profile
Moderate confidence
View the summit BGS record

Often positive when dry, but smooth, polished or slabby sections can become markedly more slippery when damp. Summit-point bedrock mapping; the actual route may cross different rock, superficial deposits, polish, lichen or seepage.

Generic exposed scrambling terrain; mapped summit-point bedrock is included where available, but route grade, exact rock, polish, drainage and escape options remain unresolved. Contains British Geological Survey materials © UKRI 2026. How to use the climbing and scrambling forecast.

Did this match your experience?Tell us about the rock surface and wind to help improve this beta forecast.Give feedback

A broad surface report is enough; you do not need to identify a particular route.

Overnight · Aurora, stars & meteorsAfter darkBetaCloud is likely to obscure much of the sky. Rain may interrupt viewing. Moonlight washes out fainter stars. View forecastClose forecast

After dark: aurora and stargazing

Night beginning 2026-09-27. All times are UK local time.

Aurora outlook

No significant activity expected.

A broad activity outlook, not a forecast of a visible display. Cloud and activity can change before the night.

Stargazing

Poor sky conditions during the best available spell: 27 Sep, 21:00 BST to 22:00 BST.

Cloud is likely to obscure much of the sky. Rain may interrupt viewing. Moonlight washes out fainter stars.

A bright Moon remains above the horizon through full darkness, washing out fainter stars and meteors.

Sky conditions through the night
Fully dark periods. Conditions can change between forecast hours.
TimeViewing conditions
27 Sep, 21:00 BST to 22:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Rain may interrupt viewing. Moonlight washes out fainter stars.

27 Sep, 22:00 BST to 23:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Rain may interrupt viewing. Moonlight washes out fainter stars.

27 Sep, 23:00 BST to 28 Sep, 00:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Rain may interrupt viewing. Moonlight washes out fainter stars.

28 Sep, 00:00 BST to 01:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Rain may interrupt viewing. Reduced visibility may obscure faint objects. Moonlight washes out fainter stars.

28 Sep, 01:00 BST to 02:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Reduced visibility may obscure faint objects. Moonlight washes out fainter stars.

Limited model coverage.

28 Sep, 02:00 BST to 03:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Moonlight washes out fainter stars.

Limited model coverage.

28 Sep, 03:00 BST to 04:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Moonlight washes out fainter stars.

Limited model coverage.

28 Sep, 04:00 BST to 05:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Moonlight washes out fainter stars.

Limited model coverage.

28 Sep, 05:00 BST to 05:15 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Moonlight washes out fainter stars.

Limited model coverage.

Moon, darkness and meteor showers

Near-full moon, about 98% illuminated.

Moonrise around 27 Sep, 18:55 BST.

Full darkness: 27 Sep, 21:00 BST to 28 Sep, 05:15 BST.

Moon times assume an open horizon. Hills can hide the Moon sooner. Moon-free does not mean cloud-free.

Southern Taurids are active on this night. Activity may be much lower away from the peak.

  • Draconids: peak around 9 October 2026.
  • Southern Taurids: peak around 10 October 2026.
  • Orionids: peak around 21 October 2026.
  • Northern Taurids: peak around 12 November 2026.
  • Leonids: peak around 18 November 2026.
  • Geminids: peak around 14 December 2026.
  • Ursids: peak around 22 December 2026.

Dates from the Royal Observatory Greenwich. Activity dates do not guarantee visible meteors. Look across a broad, dark sky, not only north.

Darkness of the surroundings

Estimated darkness rank 470 of 980 assessed peaks (1 is darkest), based on surrounding artificial light in 2021. This is not a measurement of tonight’s sky.

2021 artificial-light baseline, not measured sky brightness or a Bortle class. Changes to lighting, blue-rich LEDs, terrain screening, atmospheric scattering and cloud-reflected light are not resolved. Similar ranks are not meaningfully distinct. Darkness is not a recommendation to climb a summit at night.

VIIRS nighttime lights: Earth Observation Group, Payne Institute for Public Policy, Colorado School of Mines. Reprocessed by OpenGeoHub/OpenLandMap. Cropped and ranked by Mountain Weather.

Sky-weather grades exclude light pollution, terrain and thin haze. They are not mountain safety ratings. Check the mountain and camping forecast separately. Accessible lower viewpoints may be a better choice than summits.

Recommended kit for this dayWeather-aware packing prompts, plus your core hillwalking kitView kit

For a day hillwalk, not a complete route-specific checklist. Carry navigation and backup you can use, warm and waterproof layers, suitable footwear, food and water, a headtorch, emergency shelter, first aid and a way to call for help. Snow, ice, technical terrain and overnight trips need additional equipment and skills.

Does the weather shape your plans?Optional hill-user research. One answer helps; further questions are up to you.Take part

Help the Mountain Decisions Project understand how forecasts influence hill days, including when plans stay the same. Findings will be shared publicly as summaries, not individual responses.

This is about Diffwys on Sunday 27 September 2026. It asks about intentions, not whether you actually went out. No name or account is needed.

Open the questions to take part.

About the research and your privacy · Already been out? Share that experience instead

Confidence: Unavailable
Overall hill weather80/100Good
Wind10-25 mph southwesterly Gusts25-35 mph Feels like0 to 4°C PrecipitationAround 2-5 mm Cloud-free summit estimate80% Freezing levelAbove summit DaylightSunrise 07:11 · Sunset 19:01 · 11.8 hours daylight

The day on the hill

A wet day on Diffwys: summit wind broadly 10-25 mph, with gusts 25-35 mph at times (a fresh breeze).

Wind & exposure

Much calmer lower down - generally 5-15 mph in the valley, rising towards the tops.

Cloud & views

Cloud base around 800–1100 m in the morning, lifting to 1000–1300 m around midday. The summit is likely to stay mostly clear.

Cloud-height uncertainty could put the summit in or out of cloud. Clear spells may be difficult to time.

Drizzle is forecast for much of the day. The forecast total is around 2-5 mm, but local amounts will vary.

Forecast models differ on summit wind strength. Treat the wind figures as a guide.

Exposed tops may feel chilly in the wind. A windproof layer will help, with an extra warm layer for stops.

If clothing gets wet, you can cool more quickly. Keep a dry warm layer protected.

Forecast confidence

Overall confidence is unavailable: insufficient comparable wind, rain guidance.

Cloud-free timing: Around 60% early, improving to around 85% later.

Sunshine context Model-grid estimate, not summit sunshine

The surrounding model grid indicates 10.9 h of sunshine. This is not a forecast of time in sunshine on the summit. Use the cloud and views outlook above for the conditions on this mountain.

Early
2 h
Midday
4 h
Later
2.9 h

Overnight forecast: 17:00–08:00 (UK local time), in Wild camping below.

Morning · 08:00–12:00 Good Summit winds around 10-20 mph. Gusts around 15-25 mph are possible on exposed ground. Rain is forecast during this period.
77/100
Afternoon · 12:00–17:00 Good Summit winds around 10-20 mph. Gusts around 20-30 mph are possible on exposed ground. Rain is forecast during this period.
83/100

Compare an early start with later conditions. The main forecast above covers the day in more detail.

Overnight · 17:00–08:00Wild campingBetaAbout 2.2 mm is forecast, with rain possible around pitching time. 64/100Mixed · 600 m View detailsHide details
Night beginning Monday 28 September 2026

Full overnight outlook

Open-hillside camping looks reasonable overall around 600 m (64/100). It may be breezy on open ground, with gusts near 25 mph. Around 2.2 mm is forecast, including rain around pitching time. Condensation risk is high near 300 and 600 m, so a wet pack-up is possible. Ventilation will matter.

Overnight rain2.2 mm Open ground · 600 m14 mph · gusts 26 mph Morning pack-upDampness possible Sleeping-bag warmthISO comfort rating about 2°C or lower

Moon overnight

Waning gibbous moon

Illuminated disc
94%
Moonrise
19:07 BST
Moonset
Outside this window

Extensive cloud may limit moonlight. Illumination describes the sunlit part of the Moon, not brightness at your pitch.

Overnight window: 28 Sep, 17:00 BST to 29 Sep, 08:00 BST. Approximate open-horizon times; hills can hide the Moon. Still take a headtorch.

Elevation reference (open ground)

300 m64/100 · reasonable
Wind / gust
12 mph / 22 mph
Typical / low
6.8°C / 5.5°C · much of the night
In cloud
0% of modelled night
Condensation
High
600 m64/100 · reasonable
Wind / gust
14 mph / 26 mph
Typical / low
6.8°C / 5.5°C · much of the night
In cloud
0% of modelled night
Condensation
High

Warmth planning: As a broad starting point, consider a 3-season bag with an ISO/EN comfort rating at or below about 2°C. Allow more margin if you sleep cold or expect fatigue, and use an adequate insulated mat. Dampness is possible, so keep the sleep system dry and ensure its insulation remains effective if damp.

Open-hillside reference. A sheltered pitch may be calmer; cols and ridges may be much windier. Tent design and the exact pitch still matter. Read about sleeping-bag comfort ratings, pitching in strong winds or using the wild-camping forecast.

Did this match your night?Share a quick observation to help improve this beta forecast.Give feedback

Approximate height is enough, please do not share an exact wild-camp location.

Daytime · exposed rockClimbing & scramblingBetaWet rock is likely. Mixed51/100 View detailsHide details
Generic exposed-rock guidance

Full climbing & scrambling outlook

Conditions for exposed scrambling look mixed (51/100). Rain during the climbing period is likely to leave rock wet and more slippery. The mapped summit rock is Mudstone and siltstone (Gamlan Formation). Often positive when dry, but smooth, polished or slabby sections can become markedly more slippery when damp.

Rock surfaceWet rock likelyPeak gust29 mphRain2.2 mm
Main concernwet rock likely
Mapped summit rock Mudstone and siltstone Gamlan Formation
Origin
Sedimentary
Rock family
Slate or mudstone
Mapping
BGS Geology 50K · 1:50,000
Rock-response profile
Moderate confidence
View the summit BGS record

Often positive when dry, but smooth, polished or slabby sections can become markedly more slippery when damp. Summit-point bedrock mapping; the actual route may cross different rock, superficial deposits, polish, lichen or seepage.

Generic exposed scrambling terrain; mapped summit-point bedrock is included where available, but route grade, exact rock, polish, drainage and escape options remain unresolved. Contains British Geological Survey materials © UKRI 2026. How to use the climbing and scrambling forecast.

Did this match your experience?Tell us about the rock surface and wind to help improve this beta forecast.Give feedback

A broad surface report is enough; you do not need to identify a particular route.

Overnight · Aurora, stars & meteorsAfter darkBetaNight-sky guidance is unavailable for this night. View forecastClose forecast

After dark: aurora and stargazing

Night-sky guidance is unavailable for this night. This does not mean clear skies or no aurora.

Recommended kit for this dayWeather-aware packing prompts, plus your core hillwalking kitView kit

For a day hillwalk, not a complete route-specific checklist. Carry navigation and backup you can use, warm and waterproof layers, suitable footwear, food and water, a headtorch, emergency shelter, first aid and a way to call for help. Snow, ice, technical terrain and overnight trips need additional equipment and skills.

Does the weather shape your plans?Optional hill-user research. One answer helps; further questions are up to you.Take part

Help the Mountain Decisions Project understand how forecasts influence hill days, including when plans stay the same. Findings will be shared publicly as summaries, not individual responses.

This is about Diffwys on Monday 28 September 2026. It asks about intentions, not whether you actually went out. No name or account is needed.

Open the questions to take part.

About the research and your privacy · Already been out? Share that experience instead

Weather data: Open-Meteo (CC BY 4.0). Adapted by Mountain Weather.

Forecast run: 2026-09-21

Keep exploring

Weather around Diffwys.

Compare the summit forecast with the wider regional picture and nearby peaks before choosing a route.

Regional mountain forecastEryri (Snowdonia)View area →
Y Llethr756 m · 2.4 km awayForecast →Rhinog Fach712 m · 3.6 km awayForecast →Y Garn629 m · 4.2 km awayForecast →Rhinog Fawr720 m · 5.6 km awayForecast →

A forecast is part of the decision.

Mountain weather can differ sharply from conditions in the valley. Check official warnings, carry appropriate navigation and clothing, and be ready to change the plan. Read how Mountain Weather forecasts are produced and where their limits lie.

Choose another summit